The present invention relates generally to floating offshore production vessels for oil and gas, and in particular, to a deepwater spar vessel for ice flow conditions.
The arctic regions of the world are known to contain appreciable hydrocarbon reserves (petroleum and natural gas), and exploitation of these reserves is likely to occur in the near future. Some of these hydrocarbon reserves are in deep water, and currently there is not a proven floating system for the production of petroleum and natural gas from deep water in areas where ice flow conditions are common.
Icebergs and ice flow conditions existing in the arctic regions create a major hurdle to deepwater drilling operations. Ice flow from sheets of ice is caused by environmental forces, such as water currents and wind acting on the ice. A drilling platform may be severely damaged if left to take the full impact of the crushing force of ice flow conditions or left to suffer a collision with an iceberg.
Drilling platforms not suited for ice flow conditions must be removed to safer waters until the ice is sufficiently melted. Many work hours as well as production hours are lost during removal of a drilling platform as a result of severe ice flow conditions or an approaching iceberg.
Previous systems exist that melt or break ice flow as the ice flow approaches the drilling platform. Other systems suggested are structures that are physically capable of withstanding the crushing forces of ice flow. Still other systems use structures that merely redirect ice flow. These systems are typically costly and/or impractical. Further, these systems do not provide an efficient means for removal of the drilling platform in the face of an imminent iceberg collision.
Of the several generic types of offshore platforms for the exploitation of undersea hydrocarbon reserves, the spar-type platform is most promising for arctic conditions, since it has a smaller water plane area than other designs, and thus has a smaller hull section exposed to ice flows. Nevertheless, spar-type platforms can still suffer damage by ice flows, and destruction by icebergs, and are thus not suitable, in their present state of the art, for areas where these phenomena are prevalent.
A need therefore exists for a drilling platform system that can be quickly and efficiently moved temporarily to avoid an imminent iceberg collision, and that can still be quickly and easily restored to its original operation position after the possible danger has passed. It would also be advantageous to provide such a platform with the ability to withstand ice flow conditions.